This invention relates generally to digital memory systems and more particularly to digital memory systems which are adapted to store radio frequency signals and to enable subsequent retransmission of such signals.
As is known in the art, it is frequently desired to store a received radio frequency signal and later retransmit such signal. One digital memory system used for such retransmission is described in U.S. Pat. No. 4,318,183 issued Mar. 2, 1982, entitled "Multiple Channel Digital Memory System", inventors Roy E. Byington and William M. Pease, and assigned to the present assignee as the present invention. As discussed in such U.S. Pat. No. 4,318,183, to satisfy the Nyquist sampling criterion, the samples of the received signal should be taken at twice the bandwidth of the digital memory. Thus, if the maximum operating sampling rate of the digital memory is 2f.sub.c, the maximum bandwidth of the digital RF memory is f.sub.c. It follows, then, that for applications requiring operation over a relatively large bandwidth and storage of samples of relatively long received signals, the storage capacity of the memory may become excessively large and expansive. One technique suggested to reduce storage capacity is to scan a narrow band memory system sequentially in time over different portions of the entire required operating bandwidth, such as by mixing the received signal with a local oscillator signal having a sequentially stepping frequency; however, the use of such arrangement is relatively costly and complex.